If you're looking for a hardener to replace chrome alum, glutaraldehyde is superb. It is often used as a sterilant by tattoo artists. 1 ml of a 2.5% solution will thoroughly harden 10 grams of gelatin (i.e. 100 ml of 10% gelatin solution).

Originally Posted by MDR

The problem with cadmium is that it's near impossible to get it in the EU and so are a lot of other products necessary for the production of serious emulsions
Under the guise of safety and environment the EU is very anti chemistry and homebuild products (safety and environment my behind) In Austria I can't even get chromium alum.
These sad facts are imo the main cause for the lack of interest in emulsion making in Europe we all like to do it but we can't. Aside from very simple emulsions that is.